Electrochemical co-deposition of phosphonate-modified carbon nanotubes and tantalum on Nitinol

Nitinol substrates are coated with thin surface films made of carbon nanotubes (CNTs) and tantalum (Ta), with the aim of fostering their osseointegration aptitudes. Exceptional mechanical and chemical characteristics of CNTs combined with the resistance to corrosion and strong bioactive properties of tantalum allow for the generation of adherent, protective and functional layers on metallic biomaterial platforms. The composite coatings are elaborated on Nitinol through a two-step electrochemical protocol; firstly, through the electrophoretic deposition of phosphonate-modified CNTs and, secondly, with electrodeposition of Ta. As a preliminary step, phosphonate groups, acting, in addition, as specific Ta-capture entities, are introduced on the CNT sidewalls by means of diazonium derivatives, which imply no hard oxidative treatment. X-ray photoelectron spectroscopy as well as scanning and transmission electronic microscopies are used to analyse the chemical composition, structure and morphology of the different layers.